In general chemical processes, heat exchange is performed in various routes which pass through reactors or distillation columns and waste heat generated after heat exchange may be reused or wasted. For example, as shown in FIG. 1, when the waste heat is a low-level heat source in a sensible heat state at a temperature of less than 100° C., for example, 50 to 90° C., the waste heat is unable to be substantially reused due to the excessively low temperature thereof, thereby being condensed by condensate water and then wasted.
Meanwhile, low pressure or high pressure steam is variously used. Particularly, high temperature and high pressure steam is generally used in chemical processes. Generally, atmospheric pressure and room temperature water is heated to the evaporation point and high pressure is applied to the water converted into steam to increase internal energy, thereby generating high temperature and high pressure steam. In this case, to evaporate water in a liquid state, a large amount of energy consumption is necessary.